The purpose of this proposal is to develop a cell culture technique with potential to predict acute human chemical toxicity. The ability of the method to assess human toxicity will be determined using several indicators of general cytotoxicity, including cell proliferation and viability, protein and lipid synthesis. The agents to be evaluated are derived from a list of 50 reference chemicals having defined acute human lethal blood concentrations and well established rodent LD50 values. The reference list has been suggested by the Multicenter Evaluation for In Vitro Cytotoxicity (MEIC) Program. The Program is organized by the Scandinavian Society of Cell Toxicology to coordinate international laboratory testing of chemicals for the purpose of developing in vitro alternatives to animal experimentation. Short-term and long-term exposures, intermittent repeated dosages, and chronic exposures during several passage levels, will be performed with continuous lung and dermal cell lines. Dose-response curves will be generated from the testing of each chemical and the data will be subjected to linear regression analysis, from which the 50% inhibitory concentration (IC50) is extrapolated. In addition to regression analysis, the coefficient of correlation ("r" value), standard error of the X and Y estimates, and the t-test for linearity, are calculated and used to determine statistical significance (95% and 99% confidence intervals). The results will be compared to known animal toxicity data and human toxic and lethal concentrations. Experimental values will also be submitted to the MEIC committee which is responsible for validation of the data, as well as the interlaboratory reproducibility. It is anticipated that this cell culture technique will supplement, support or replace currently used procedures to determine rodent LD50 values. The protocol has the potential to screen compounds possessing general or organ-specific toxicities and will be an important component of a battery of tests used to predict human toxicity.